1. Field of the Invention
The invention relates to a figure digitizing system.
2. Description of the Related Art
Computer-Aided Design (CAD) systems which draw and manage graphic figures under computer control are becoming more and more popular. Thus, figure digitizers are needed as input means for these CAD systems.
A generally known figure digitizing system is designed such that the operator traces a figure drawn on a drawing with an image reading cursor and presses a key provided on the image reading cursor at the intended position of the figure. The system recognizes and records the coordinates of the cursor position.
However, this general digitizing system requires the operator to accurately set the cursor position on the intended point. Therefore, a significant amount of physical and mental effort is required by the operator during the image input operation. In addition, the accuracy of the input data varies greatly depending on the degree of proficiency of each operator. This causes various problems when the CAD system uses the input data.
Another known figure digitizing system comprises an image scanner, a display unit which displays the image data produced by the image scanner, and a mouse device used to point to an arbitrary position of the displayed image. In operation, the system displays candidate digitizing points on a displayed line of the image, and the operator selects a point with the mouse. The position of the selected point is then digitized and stored.
This figure digitizing system reads the entire drawing to enter a figure. Therefore, this system requires a large image scanner, which results in an expensive, large-scale system. In addition, a long time is needed read a large, intricate drawing. Further, a large memory capacity is needed to store the input image data.
A known automatic figure digitizing system, which is intended to relieve the operator's labor, is designed to read the entire drawing with a scanner, analyze the generated image data, automatically extract all characteristic points of the figures included in the drawing, and calculate the coordinates of the points of the drawing figures.
This automatic figure digitizing system suffers from degraded reliability and accuracy of the input data when the points and lines drawn on the drawing are not clear. Hand-written figures are particularly prone to this problem.
Because of these problems, an operator expends a significant amount of time and labor when entering the drawings which become source data for the system. In order to effectively use the vast amount of existing drawings, CAD operators desire a drawing input means which is both easy to operate and accurate enough to efficiently transform drawings figures into electronic data usable as source CAD data.